Single-Dose vs. Divided-Dose G-CSF for Stem Cell Mobilization in Healthy Allogeneic Donors

National and international guidelines/consensus recommend G-CSF (granulocyte colony-stimulating factor) at 10 μg/kg/day as a single daily dose or divided into two daily doses for mobilization in healthy donors for allogeneic hematopoietic stem cell transplantation. However, there is no consensus or standard regarding single versus divided dosing, and high-quality evidence is lacking. Existing randomized controlled trials have small sample sizes and inconsistent conclusions, and none have focused on Asian population characteristics (e.g., body weight and drug metabolism differences). This study aims to provide level I evidence to optimize donor experience and define the optimal administration strategy. Inclusion criteria: Healthy allogeneic stem cell donors aged 18-60 years, meeting institutional standard donor screening criteria (HLA matching, normal blood counts, normal liver and kidney function, negative infection screening), and providing written informed consent. Primary endpoint: The rate of achieving a first apheresis yield of ≥ 4 × 10⁶ CD34⁺ cells/kg (donor body weight) after 5 days of G-CSF mobilization. Secondary endpoints: The rate of achieving ≥ 2 × 10⁶ CD34⁺ cells/kg with at most one apheresis; time to myeloid, platelet, and erythroid engraftment in recipients; the proportion and composition of immune cells (CD34⁺, CD3⁺, CD19⁺, CD56⁺, etc.) in the apheresis product; donor adverse events; donor-reported outcomes; and the difference in CD34⁺ stem cell yields between single-dose and divided-dose mobilization. Intervention: G-CSF will be administered at a total dose of 10 μg/kg/day, either as a single daily injection or divided into two equal daily injections. This study is designed to investigate whether single-dose or divided-dose G-CSF administration is superior for mobilizing healthy donors in allogeneic hematopoietic stem cell transplantation.